Question: $\dfrac{7}{4} - \dfrac{7}{10} = {?}$
$ = {\dfrac{7 \times 5}{4 \times 5}} - {\dfrac{7 \times 2}{10 \times 2}} $ $ = {\dfrac{35}{20}} - {\dfrac{14}{20}} $ $ = \dfrac{{35} - {14}}{20} $ $ = \dfrac{21}{20}$